Every guy has his own theory about which exercises are the best and which exercises suck. Whether we're analyzing the biomechanics of an exercise (not very likely), "feeling the burn" (more likely), or simply doing a ton of sets and seeing how sore we get over the next few days (ding, ding, ding, we have a winner!), we all think we know the best movements to grow our muscles.

But do we really?

Bret Contreras wants to take you inside your muscles–without the freak accident that usually precedes such gross anatomy lessons–using EMG, a tool that measures how much muscle activity is going on with every movement you do.

After testing 25 different shoulder and trap exercises, he's here to reveal the best of the best.

Before we get started, I want to say I'm not going to make any judgments regarding the safety of any exercise in this article. I realize that certain exercises pose greater risks to the joints than others, but every guy has the right to train however the hell he chooses. As lifters, we can choose to assume a lot of risk or little risk since we're the owners of our bodies. So keep that in mind before you type me nasty letters.

Now, are you ready to learn the best exercises to build boulder shoulders and monster traps?

I'll clear up a few science-y things first and then hit you with the results! (If you skip down to view the exercises first, I don't blame you. But make sure to come back up here to read how it works!)

What The Heck Is EMG Anyway?

EMG measures the electrical activity of muscles during exercise. While EMG doesn't directly measure muscular tension, the two should be very similar (although slightly off-set), as the electrical activity that EMG measures is simply a measurement of the nervous system's signal to the muscles. Increased EMG activity is indicative of the nervous system's attempt to produce more muscular force. (That's a good thing, by the way.) I used a Myotrace 400 from Noraxon to measure the EMG of every exercise.

What's MVC?

MVC stands for Maximum Voluntary Contraction. It's a measurement of how hard a muscle can contract isometrically. When you record MVC, you simply position your body in an advantageous position and squeeze your muscle as hard as possible. You can also push against an immovable object.

Each muscle has its own position that will yield the highest electrical value. The first step in measuring EMG activity is recording MVC. Following this recording, every subsequent exercise performed will be compared to MVC as a percentage.

What Are Mean And Peak Activation?

For each exercise I tested, I received data that showed both the mean activation and the peak activation.

Researchers typically use mean MVC for their data. I used to think that mean activation was more important as it measured the average activation throughout the entire repetition. However, muscles are not always active throughout the entire range of motion of an exercise, especially during compound lifts.

For example, one muscle might be very active down low in the stretched position, while another muscle becomes more active up top in the contracted position of the same exercise.

For this reason I believe that peak MVC is a more important figure. Peak activation is a measurement of the highest point of activation during the repetition.

Still, I believe that mean activation might be more important for bodybuilding purposes in providing constant tension, occlusion, and "the pump," while peak activation might be more important for sport-specific purposes in providing maximum tension at a certain moment for peak force production.

Got it so far? Good.

How Is It Possible To Exceed 100% of MVC?

I would hope that a guy like myself with 18 years of lifting experience could exceed MVC (which is an isometric contraction) through dynamic barbell, dumbbell, band, or bodyweight exercises. If we couldn't exceed MVC through lifting, then we'd build a strong case for isometric bodyweight training (a la Charles Atlas) for bodybuilding purposes.

The reality is that strength training exercises will typically cause peak activation to far exceed MVC. If the exercise is really good, mean activation can exceed MVC as well. When this happens, it simply means that the average activation throughout the repetition is higher than the average activation recorded from a maximum isometric voluntary contraction.

People Are Different, But Not That Different.

Having measured the EMG of several individuals, I've realized that everyone is different, but not that different. The two most influential factors in muscle activation differences are anthropometry and form.

For example, taller individuals tend to exhibit more glute activity during squats than shorter individuals. This makes sense when you think about it, since they have farther to travel. As another example, a powerlifting-style bench press will yield much less pec activity than a bodybuilding-style bench press since the elbows are kept tucked.

Although the length of one's body segments and the manner in which one performs an exercise can impact muscle activation, it's surprising how similar most individuals' activations are when it comes to strength training.

More Research Is Needed.

The data used in this article was obtained from one individual (me) during a week-long series of experiments. I'd hook up the electrodes to the muscle parts I wanted to measure and then perform all the exercises in one session to allow for the greatest level of accuracy.

The only exception was for the glutes, quads, adductors, and hamstrings, which required three different tests: one for strength exercises, one for explosive exercises, and one special test for the different areas of the glutes. (Shut up. I'm the Glute Guy after all!)

By no means am I trying to suggest that this article should be the definitive Bible on muscular development. Each time I embark on a new series of EMG experiments I learn a tremendous amount of information. I will continue to experiment and share my findings as I acquire new bits of knowledge.

Althought it's clear more EMG research and experimentation is needed to confirm the results of my studies, this article is (I hope) very telling in terms of exercise efficiency.

Can An Exercise Target a Specific Portion of a Muscle?

My EMG research indicates that the bodybuilders were right: various exercises can stress different parts of muscles.

For years we've known the different heads of certain muscles such as the deltoids and pectoralis major function differently from one another. However, my research indicates that muscle fibers within a muscle can function differently from one another even if they don't have separate heads. For example, during my research I noted that the upper rectus abdominis and lower rectus abdominis function differently.

I suspect that this is true of all muscles, as muscles often have varying fiber angles and attachment points, numerous motor units, and sometimes varying nerve suppliers.

This might explain why lifters tend to see better results when they incorporate variety into their routines rather than sticking to just one exercise per muscle or movement pattern.

The Second Rep

Another significant finding that I encountered is that during a heavy set, the second rep nearly always produced higher EMG readings than the first rep. Perhaps the nervous system "figures out" how to better recruit the muscles following the first repetition. This might explain why Olympic lifters and powerlifters see better results when they perform multiple (albeit low) repetitions rather than just heavy singles, or just why the I, Bodybuilder program seems to be so effective.

What You've Been Waiting For! The Exercises.

Since this is a bodybuilding experiment, I never used a weight that was too heavy to perform at least five repetitions. The mean number is on top and the peak number is on bottom. (If you don't know what I'm talking about, make sure to read "What Are Mean And Peak Activation?" above.)

Exercise

Upper Trap

Anterior Delt

Lateral Delt

Posterior Delt

45 lb Standing Military Press

60.1117.0

65.5145.0

8.923.7

4.08.3

135 lb Standing Military Press

56.199.0

120.0266.0

23.968.0

7.616.7

155 lb Standing Military Press

47.482.3

131.0315.0

25.486.6

7.818.8

175 lb Standing Military Press

53.481.2

150.0281.0

34.087.7

9.621.5

155 lb Standing Behind Neck Press

66.594.0

146.0318.0

45.788.7

13.923.6

70 lb DB Standing Military Press

51.693.0

174.0432.0

43.3111.0

14.543.1

135 lb Seated Shoulder Press

65.698.1

120.0221.0

23.858.9

7.914.9

185 lb Seated Shoulder Press

67.291.6

190.0311.0

48.794.3

13.219.9

165 lb Seated Behind Neck Press

72.1110.0

274.0471.0

69.5106.0

17.627.8

80 lb Seated DB Shoulder Press

60.5106.0

162.0328.0

43.587.3

13.821.4

50 lb Dumbbell Upright Row

58.4113.0

60.6119.0

56.1102.0

54.3103.0

60 lb Dumbbell Upright Row

38.259.9

57.8146.0

61.696.3

71.1138.0

75 lb Cable Upright Row

60.7109.0

37.492.6

46.587.6

54.0147.0

135 lb Barbell Upright Row

53.767.4

96.6204.0

68.0102.0

80.9155.0

95 lb Barbell Upright Row

64.391.9

69.9125.0

54.7100.0

65.6139.0

30 lb Lateral Raise

49.283.2

80.8170.0

73.4148.0

63.5113.0

40 lb Lateral Raise

41.777.3

113.0191.0

83.1141.0

73.3134.0

50 lb Lateral Raise

44.9101.0

114.0213.0

84.3124.0

66.3133.0

40 lb Cable Lateral Raise

75.5150.0

55.2163.0

58.4136.0

64.2121.0

30 lb Dumbbell Front Raise

66.4104.0

105.0202.0

49.476.1

39.584.5

55 lb Barbell Front Raise

64.4101.0

99.3170.0

36.870.5

31.174.3

30 lb DB Bent Over Rear Delt Raise

31.279.0

13.842.7

46.9103.0

94.2182.0

50 lb DB Bent Over Rear Delt Raise

40.387.6

19.441.6

60.5108.0

94.7153.0

25 lb DB Prone Rear Delt Raise

43.991.1

18.753.3

64.3126.0

88.9152.0

30 lb Cable Scarecrow

50.998.8

29.168.7

62.8130.0

93.8167.0

Bodyweight Push Up

11.629.9

88.3175.0

12.924.5

5.712.1

225 lb Bench Press

4.820.5

97.8201.0

7.017.3

5.88.4

Bodyweight Dip

3.39.8

21.139.2

3.14.7

9.820.6

225 lb Incline Press

40.569.1

184.0390.0

24.945.5

7.911.7

Bodyweight Pull Up

17.856.3

14.135.4

4.514.4

19.153.2

Bodyweight Chin Up

12.742.9

15.174.7

6.433.0

17.264.9

Bodyweight Hanging Row

12.924.4

12.233.2

35.779.6

87.1182.0

100 lb Dumbbell Shrug

29.257.7

9.122.2

20.239.7

42.693.6

50 lb Dumbbell Shrug

39.562.9

10.323.3

11.921.6

27.254.1

120 lb Face Pull

69.7101.0

16.829.2

55.092.8

87.1159.0

Band Face Pull

60.177.1

21.137.1

90.7152.0

144.0252.0

225 lb Barbell Shrug

76.1118.0

17.031.5

9.918.5

29.666.0

225 lb Behind Back Shrug

39.567.1

11.621.1

19.338.2

45.171.6

315 lb Barbell Shrug

81.9145.0

18.032.1

24.646.8

48.372.8

The Winners

Based on this experiment, here are the top three exercises in terms of mean and peak activity for each muscle part:

Confirmations

It's no surprise that variations of military presses and incline presses appear to be the best front delt exercises. It's also no surprise that variations of lateral raises and presses top the charts for mean and peak mid delt exercises.

Naturally we'd expect to see variations of rear delt raises and rows topping the charts in mean and peak rear delt activity. Finally, it's not shocking to see the barbell shrug at the top of the list in mean upper trap activity.

Now let's move into the stuff that shocked the hell out of me.

Surprises

I always figured the front military press worked more anterior deltoid than the behind-the-neck press, but I was definitely wrong.

And while I knew band face pulls worked the delts, I always assumed they were targeting the rear delts. I was very surprised to find that the band face pull worked more mean and peak lateral delt than any other exercise!

(It's important to know that I perform the band face pull in a special manner, making it a mixture between a face pull and a pull-apart. I grab hold of the bands with my hands about three inches apart, and as I perform the face pull motion, I pull the band apart vigorously.)

I was also very shocked to find the band face pull worked more mean and peak rear delt muscles than any other exercise, as I assumed a rear delt raise or row variation would have outperformed them.

Finally, although I was aware the upper traps got worked through a variety of shoulder exercises, I had no idea as to the magnitude of upper trap activity that was involved in typical shoulder exercises like military presses and lateral raises. I mean, the cable lateral raise topped the charts in peak upper trap activity, beating out heavy shrugs!

What If...?

During experiments like this, one is often left with much curiosity. What if I would have performed a close-grip bench press or close-grip incline press? Would they have elicited a lot of front delt activity?

What if I would have experimented with different types of grips on dumbbell military presses or different form alterations of lateral raises? How would that have impacted mid delt activity?

What if I would have done different rowing exercises or different form alterations of rear delt raises? Would they have elicited a lot of rear delt activity?

What if I would have performed push presses with a controlled eccentric? What if I had placed the electrodes in a different spot on the upper traps? How would machine exercises faired? Just who the hell is John Galt?

Clearly more research is needed, as it's impossible to anticipate everything prior to an experiment no matter how prepared and organized you seem.

The Best Damn Shoulder and Trap Workout

Based on the results of this experiment, I bet the following would be one kick-ass workout that'd target the front, mid, and rear delts as well as the upper traps. Enjoy!